Preparation of epsilon-phase silver vanadium oxide from gamma-phase SVO starting material

ABSTRACT

The current invention relates to the preparation of an improved cathode active material for non-aqueous lithium electrochemical cell. In particular, the cathode active material comprises ε-phase silver vanadium oxide prepared by using a γ-phase silver vanadium oxide starting material. The reaction of γ-phase SVO with a silver salt produces the novel ε-phase SVO possessing a lower surface area than ε-phase SVO produced from vanadium oxide (V 2 O 5 ) and a similar silver salt as starting materials. Consequently, the low surface area ε-phase SVO material provides an advantage in greater long-term stability in pulse dischargeable cells.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional of application Ser. No.10/004,995, filed Dec. 5, 2001, which claims priority based onprovisional application Ser. No. 60/254,918, filed Dec. 12, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to the conversion of chemical energy toelectrical energy. More particularly, this invention relates to thepreparation of an improved cathode active material for non-aqueouslithium electrochemical cells, and still more particularly, a cathodeactive ε-phase silver vanadium oxide (SVO, Ag₂V₄O₁₁) prepared using aγ-phase silver vanadium oxide (Ag_(1.2)V₃O_(8.1)) starting material. Theproduct cathode active material can be used in an implantableelectrochemical cell, for example of the type powering a cardiacdefibrillator, where the cell may run under a light load for significantperiods interrupted from time to time by high rate pulse discharges.

[0004] The reaction of γ-phase SVO with a source of silver producesε-phase SVO that possesses a lower surface area than SVO produced fromother vanadium-containing starting materials. The relatively low surfacearea of this new ε-phase SVO material results in greater long-termstability for the cathode active material in comparison to other formsof SVO with higher specific surfaces areas.

[0005] 2. Prior Art

[0006] The prior art discloses many processes for manufacturing SVO;however, they result in a product with greater surface area than thematerial prepared by the current invention. Specifically, U.S. Pat. No.4,391,729 to Liang et al. discloses the preparation of silver vanadiumoxide by a thermal decomposition reaction of silver nitrate withvanadium oxide conducted under an air atmosphere. This decompositionreaction is further detailed in the publication: Leising, R. A.;Takeuchi, E. S. Chem. Mater. 1993, 5, 738-742, where the syntheses ofSVO from silver nitrate and vanadium oxide under an air atmosphere ispresented as a function of temperature. In another reference: Leising,R. A.; Takeuchi, E. S. Chem. Mater. 1994, 6, 489-495, the synthesis ofSVO from different silver precursor materials (silver nitrate, silvernitrite, silver oxide, silver vanadate, and silver carbonate) isdescribed. The product active materials of this latter publication areconsistent with the formation of a mixture of SVO phases prepared underargon, which is not solely ε-phase Ag₂V₄O₁₁.

[0007] Also, the preparation of SVO from silver oxide and vanadium oxideis well documented in the literature. In the publications: Fleury, P.;Kohlmuller, R. C. R. Acad. Sci. Paris 1966, 262C, 475-477, and Casalot,A.; Pouchard, M. Bull Soc. Chim. Fr. 1967, 3817-3820, the reaction ofsilver oxide with vanadium oxide is described. Wenda, E. J. ThermalAnal. 1985, 30, 89-887, present the phase diagram of the V₂O₅-Ag₂Osystem in which the starting materials are heated under oxygen to formSVO, among other materials. Thus, Fleury and Kohlmuller teach that theheat treatment of starting materials under a non-oxidizing atmosphere(such as argon) results in the formation of SVO with a reduced silvercontent.

[0008] In U.S. Pat. No. 5,955,218 to Crespi et al., the process ofheat-treating SVO prepared by a thermal decomposition reaction toimprove the electrochemical performance of the material is disclosed. Inthis patent, thermal decomposition SVO prepared according to U.S. Pat.Nos. 4,310,609 and 4,391,729, both to Liang et al., under an airatmosphere at a somewhat lower temperature of 360° C. is described.However, the '218 patent to Crespi et al. demonstrates that adding asecond heat treatment step increases the crystallinity of the resultingactive material. The present invention is concerned with the productactive material's surface area, and not necessarily its crystallinity.

[0009] U.S. Pat. No. 5,221,453 to Crespi teaches a method for making anelectrochemical cell containing SVO, in which the cathode activematerial is prepared by a chemical addition reaction of an admixed 2:1mole ratio of AgVO₃ and V₂O₅ heated in the range of 300° C. to 700° C.for a period of 5 to 24 hours. Crespi does not discuss γ-phase SVO inthe context of this invention. Therefore, this process could notmanufacture the ε-phase material described by the current invention.

[0010] U.S. Pat. Nos. 6,130,005 and 5,955,218, both to Crespi et al.,relate to heat treated silver vanadium oxide materials, for example,γ-phase SVO heat treated to form decomposition-produced SVO (dSVO). Thestarting material does not appear to be heated for further combinationwith a source of silver or other metal. Also, U.S. Pat. No. 5,895,733 toCrespi et al. shows a method for synthesizing SVO by using AgO and avanadium oxide as starting materials. However, the result is not a lowsurface area ε-phase SVO cathode material, as disclosed in the currentinvention.

[0011] U.S. Pat. No. 5,545,497 to Takeuchi et al. teaches cathodematerials having the general formula of Ag_(x)V₂O_(y). Suitablematerials comprise a β-phase SVO having in the general formula x=0.35and y=5.18 and a γ-phase SVO having x=0.74 and y=5.37, or a mixture ofthe phases thereof. Such SVO materials are produced by the thermaldecomposition of a silver salt in the presence of vanadium pentoxide. Inaddition, U.S. Pat. No. 6,171,729 to Gan et al. shows exemplary alkalimetal/solid cathode electrochemical cells in which the cathode may be anSVO of β-, γ- or ε-phase materials. However, none of Gan et al.'smethods are capable of producing a low surface area ε-phase cathodematerial, as per the current invention.

[0012] Therefore, based on the prior art, there is a need to develop aprocess for the synthesis of mixed metal oxides, including silvervanadium oxide, having a relatively low surface area. An example is alow surface area SVO prepared using a silver-containing compound andγ-phase SVO as starting materials. The product ε-phase SVO is a cathodeactive material useful for non-aqueous electrochemical cells havingenhanced characteristics, including the high pulse capability necessaryfor use with cardiac defibrillators.

SUMMARY OF THE INVENTION

[0013] The current invention relates to the preparation of an improvedcathode active material for non-aqueous lithium electrochemical cells,and in particular, a cathode active material that contains ε-phase SVOprepared using a γ-phase SVO starting material. The reaction of γ-phaseSVO with a source of silver produces ε-phase SVO possessing a lowersurface area than ε-phase SVO produced from other vanadium-containingstarting materials. The present synthesis technique is not, however,limited to silver salts since salts of copper, magnesium and manganesecan be used to produce relatively low surface are metal oxide activematerials as well. The relatively low surface area of the ε-phase SVOmaterial provides an advantage in greater long-term stability when usedas an active cathode material compared to SVO with a higher specificsurface area.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The current invention discloses that reacting a γ-phase SVOmaterial with a source of silver, or other suitable metal salt, producespure ε-phase SVO (Ag₂V₄O₁₁). This product material possesses arelatively lower surface areas in comparison to active materialssynthesized by a thermal decomposition reaction under an oxidizingatmosphere. Decreased surface area is an unexpected result.

[0015] The thermal reaction of silver nitrate with vanadium oxide underan air atmosphere is a typical example of the preparation of silvervanadium oxide by a decomposition reaction. This reaction is set forthbelow in Equation 1:

[0016]   2AgNO₃+2V₂O₅→Ag₂V₄O₁₁+2NO_(x)  (1)

[0017] The physical characteristics of SVO material (i.e. particlemorphology, surface area, crystallinity, etc.) produced by this reactionare dependent on the temperature and time of reaction. In addition, thereaction environment has a dramatic effect on the product material. Thesame reaction of silver nitrate with vanadium oxide conducted under anargon atmosphere is depicted below in Equation 2:

2AgNO₃+2V₂O₅→AgVO₃+Ag_(1.2)V₃O₈+2NO_(x)  (2)

[0018] Thus, the synthesis of SVO under an inert atmosphere results inthe formation of a mixture of silver vanadate (AgVO₃) and γ-phase SVO(Ag_(1.2)V₃O₈). This is described in the above-referenced publication byLeising, R. A.; Takeuchi, E. S. Chem. Mater. 1994, 6, 489-495. Asreported by Leising et al., a mixture of material phases is lesssuitable than a single ε-phase SVO (Ag₂V₄O₁₁) as a cathode activematerial for lithium electrochemical cells. For this reason, argon istypically not preferred for synthesis of SVO cathode active material. Amore benign preparation technique for ε-phase SVO from vanadium oxideand silver carbonate (Ag₂CO₃) according to Equation 3 below results inthe release of CO₂ gas, which is a nontoxic byproduct. However, thespecific surface area of the product SVO is also higher than the surfacearea of SVO prepared from silver nitrate. This is shown below in Table1.

Ag₂CO₃+2V₂O₅→Ag₂V₄O₁₁+CO₂  (3)

[0019] Thus, a synthesis technique for SVO using vanadium oxide andeither silver oxide or silver carbonate, or other preferred metal salts,while eliminating the formation of toxic NO_(x) byproduct, results in anSVO material with a higher specific surface area than SVO produced fromvanadium oxide and silver nitrate. TABLE 1 Specific Surface Area ofε-Phase SVO Synthesis BET Surface Starting Materials Temperature AreaV₂O₅ + AgNO₃ 500° C. 0.42 m²/g V₂O₅ + 0.5 Ag₂O 500° C. 0.64 m²/g V₂O₅ +0.5 Ag₂CO₃ 500° C. 0.81 m²/g Ag_(1.2)V₃O_(8.1) + 0.15 Ag₂O 500° C. 0.54m²/g Ag_(1.2)V₃O_(8.1) + 0.15 Ag₂CO₃ 500° C. 0.44 m²/g

[0020] The present invention is an alternate preparation synthesis thatdoes not produce noxious by-products, such as NO_(x) and, additionally,results in an active material with a desirable relatively low surfacearea. Benefits attributed to the present synthesis process for theformation of a cathode active material are illustrated in the followingexamples:

EXAMPLE 1

[0021] In contrast to the prior art syntheses described above, SVO ofthe present invention is prepared using γ-phase SVO (Ag_(1.2)V₃O_(8.1))as a starting material instead of V₂O₅. In particular, a 12.90-gramsample of Ag_(1.2)V₃O_(8.1) was combined with a 1.09-gram sample ofAg₂O, and heated to 500° C. under a flowing air atmosphere for about 16hours. The sample was then cooled, mixed and reheated under a flowingair atmosphere at about 500° C. for about 24 hours. At this point, thematerial was cooled and analyzed by x-ray powder diffraction and BETsurface area measurements. The x-ray powder diffraction data confirmedthe formation of ε-phase SVO (Ag₂V₄O₁₁). The material displayed a BETsurface area of 0.54 m² g.

COMPARATIVE EXAMPLE 1

[0022] As a comparison, SVO was prepared by a prior art combinationreaction. In particular, a 9.00-gram sample of V₂O₅ was combined with a5.73-gram sample of Ag₂O, and heated to about 500° C. under a flowingair atmosphere for about 16 hours. The sample was then cooled, mixed andreheated under a flowing air atmosphere at about 500° C. for about 24hours. At this point the material was cooled and analyzed by x-raypowder diffraction and BET surface area measurements. The materialdisplayed a BET surface area of 0.64 m²/g, which is significantly higherthan the specific surface area of the material prepared in Example 1.

EXAMPLE 2

[0023] ε-phase SVO according to the present invention was also preparedusing a γ-phase SVO starting material in combination with silvercarbonate. In particular, a 5.00-gram sample of Ag_(1.2)V₃O_(8.1) wascombined with a 0.50-gram sample of Ag₂CO₃, and heated to about 500° C.under a flowing air atmosphere for about 16 hours. The sample was thencooled, mixed and reheated under a flowing air atmosphere at about 500°C. for about 24 hours. At this point, the material was cooled andanalyzed by x-ray powder diffraction and BET surface area measurements.The x-ray powder diffraction data confirmed the formation of ε-phase SVO(Ag₂V₄O₁₁), while the material displayed a BET surface area of 0.44m²/g.

COMPARATIVE EXAMPLE 2

[0024] As a comparison to Example 2, SVO was prepared using V₂O₅ andAg₂CO₃. In particular, a 15.00-gram sample of V₂O₅ was combined with an11.37-gram sample of Ag₂CO₃, and heated to about 450° C. under a flowingair atmosphere for about 16 hours. The sample was then cooled, mixed andreheated under a flowing air atmosphere at about 500° C. for about 24hours. At this point the material was cooled and analyzed by x-raypowder diffraction and BET surface area measurements. The materialdisplayed a BET surface area of 0.81 m²/g, which is nearly twice thespecific surface area of the material prepared in Example 2.

EXAMPLE 3

[0025] Copper silver vanadium oxide or CSVO (Cu_(0.2)Ag_(0.8)V₂O_(5.6))was prepared according to the present invention using γ-phase SVO as astarting material in combination with copper(II) oxide. In particular, a1.80-gram sample of Ag_(1.2)V₃O_(8.1) was combined with a 0.10-gramsample of CuO, and heated to about 450° C. under a flowing airatmosphere for about 16 hours. The sample was then cooled, mixed andreheated under a flowing air atmosphere at about 500° C. for about 24hours. At this point, the material was cooled and analyzed by BETsurface area measurements. The material displayed a BET surface area of0.31 m²/g.

COMPARATIVE EXAMPLE 3

[0026] As a comparison to the product of Example 3, CSVO was preparedvia the prior art decomposition method using V₂O₅, Cu(NO₃)₂ and AgNO₃.In particular, a 1.36 gram sample of V₂O₅ was combined with a 0.99 gramsample of AgNO₃ and a 0.34 gram sample of Cu(NO₃)₂•2.5H₂O, and heated toabout 400° C. under a flowing air atmosphere for about 16 hours. Thesample was then cooled, mixed and reheated under a flowing airatmosphere at about 500° C. for about 44 hours. At this point, theproduct material was cooled and analyzed by BET surface areameasurement. The material displayed a BET surface area of 0.45 m²/g,which is significantly higher than the specific surface area of the CSVOmaterial prepared in Example 3. Thus, in addition to the toxicimplications of released NO_(x) gas, the preparation of CSVO by theprior art method provides a material with a higher specific surface areathan the new preparation technique.

[0027] The above detailed description and examples are intended for thepurpose of illustrating the invention, and are not to be construed aslimiting. For example, starting materials other than silver oxide andsilver carbonate are reacted with γ-phase silver vanadium oxide to formε-phase silver vanadium compounds. The list includes: silver lactate(AgC₃H₅O₃, T_(m) 120° C.), silver triflate (AgCF₃SO₃, T_(m) 286° C.),silver pentafluoropropionate (AgC₃F₅O₂, T_(m) 242° C.), silver laurate(AgC₁₂H₂₃O₂, T_(m) 212° C.), silver myristate (AgC₁₄H₂₇O₂, T_(m) 211°C.), silver palmitate (AgC₁₆H₃₁O₂, T_(m) 209° C.), silver stearate(AgC₁₈H₃₅O₂, T_(m) 205° C.), silver vanadate (AgVO₃, T_(m) 465° C.),copper oxide (CuO, T_(m) 1,446° C.), copper carbonate (Cu₂Co₃),manganese carbonate (MnCO₃), manganese oxide (MnO, T_(m) 1,650° C.),magnesium carbonate (MgCO₃, T_(d) 350° C.), magnesium oxide (MgO, T_(m)2,826° C.), and combinations and mixtures thereof.

[0028] While the starting materials are described as being heated to apreferred temperature of about 500° C., it is contemplated by the scopeof the present invention that suitable heating temperatures range fromabout 300° C. to about 550° C., depending on the specific startingmaterials. Also, heating times for both the first and second heatingstep range from about 5 hours to about 30 hours. Longer heating timesare required for lower heating temperatures. Further, while the presentinvention has been described in the examples as requiring two heatingevents with an ambient mixing in between, that is not necessarilyimperative. Some synthesis protocols according to the present inventionmay require one heating step with periodic mixing, or multiple heatingevents with periodic ambient mixing.

[0029] The product mixed metal oxides according to the present inventionincludes: ε-phase SVO (Ag₂V₄O₁₁), CSVO (Cu_(0.2)Ag_(0.8)V₂O_(5.6)),MnSVO (Mn_(0.2)Ag_(0.8)V₂O_(5.8)), and MgSVO(Mg_(0.2)Ag_(0.8)V₂O_(5.6)). The use of the above mixed metal oxides asa cathode active material provides an electrochemical cell thatpossesses sufficient energy density and discharge capacity requiredmeeting the vigorous requirements of implantable medical devices. Thesetypes of cells comprise an anode of a metal selected from Groups IA, IIAand IIIB of the Periodic Table of the Elements. Such anode activematerials include lithium, sodium, potassium, etc., and their alloys andintermetallic compounds including, for example, Li—Mg, Li—Si, Li—Al,Li—B and Li—Si—B alloys and intermetallic compounds. The preferred anodecomprises lithium. An alternate anode comprises a lithium alloy such asa lithium-aluminum alloy. The greater the amounts of aluminum present byweight in the alloy, however, the lower the energy density of the cell.

[0030] The form of the anode may vary, but preferably the anode is athin metal sheet or foil of the anode metal, pressed or rolled on ametallic anode current collector, i.e., preferably comprising titanium,titanium alloy or nickel, to form an anode component. Copper, tungstenand tantalum are also suitable materials for the anode currentcollector. In the exemplary cell of the present invention, the anodecomponent has an extended tab or lead of the same material as the anodecurrent collector, i.e., preferably nickel or titanium, integrallyformed therewith such as by welding and contacted by a weld to a cellcase of conductive metal in a case-negative electrical configuration.Alternatively, the anode may be formed in some other geometry, such as abobbin shape, cylinder or pellet to allow an alternate low surface celldesign.

[0031] Before the previously described ε-phase active materials arefabrication into a cathode electrode for incorporation into anelectrochemical cell, they are preferably mixed with a binder material,such as a powdered fluoro-polymer, more preferably powderedpolytetrafluoro-ethylene or powdered polyvinylidene fluoride, present atabout 1 to about 5 weight percent of the cathode mixture. Further, up toabout 10 weight percent of a conductive diluent is preferably added tothe cathode mixture to improve conductivity. Suitable materials for thispurpose include acetylene black, carbon black and/or graphite or ametallic powder such as of nickel, aluminum, titanium and stainlesssteel. The preferred cathode active mixture thus includes a powderedfluoro-polymer binder present at about 3 weight percent, a conductivediluent present at about 3 weight percent and about 94 weight percent ofthe cathode active material. For example, depending on the applicationof the electrochemical cell, the range of cathode compositions is fromabout 99% to about 80%, by weight, ε-phase silver vanadium oxide mixedwith carbon graphite and PTFE.

[0032] Cathode components for incorporation into an electrochemical cellaccording to the present invention may be prepared by rolling, spreadingor pressing the cathode active materials onto a suitable currentcollector selected from the group consisting of stainless steel,titanium, tantalum, platinum, gold, aluminum, cobalt-nickel alloys,nickel-containing alloys, highly alloyed ferritic stainless steelcontaining molybdenum and chromium, and nickel-, chromium- andmolybdenum-containing alloys. The preferred current collector materialis titanium and, most preferably, the titanium cathode current collectorhas a thin layer of graphite/carbon material, iridium, iridium oxide orplatinum applied thereto. Cathodes prepared as described above may be inthe form of one or more plates operatively associated with at least oneor more plates of anode material, or in the form of a strip wound with acorresponding strip of anode material in a structure similar to a“jellyroll”.

[0033] In order to prevent internal short circuit conditions, thecathode is separated from the Group IA, IIA or IIIB anode by a suitableseparator material. The separator is of electrically insulativematerial, and the separator material also is chemically unreactive withthe anode and cathode active materials and both chemically unreactivewith and insoluble in the electrolyte. In addition, the separatormaterial has a degree of porosity sufficient to allow flow there throughof the electrolyte during the electrochemical reaction of the cell.Illustrative separator materials include fabrics woven fromfluoropolymeric fibers including polyvinylidine fluoride,polyethylenetetrafluoroethylene, and polyethylenechlorotrifluoroethyleneused either alone or laminated with a fluoropolymeric microporous film,non-woven glass, polypropylene, polyethylene, glass fiber materials,ceramics, a polytetrafluoroethylene membrane commercially availableunder the designation ZITEX (Chemplast Inc.), a polypropylene membranecommercially available under the designation CELGARD (Celanese PlasticCompany, Inc.) and a membrane commercially available under thedesignation DEXIGLAS (C. H. Dexter, Div., Dexter Corp.).

[0034] The electrochemical cell of the present invention furtherincludes a nonaqueous, ionically conductive electrolyte that serves as amedium for migration of ions between the anode and the cathodeelectrodes during the electrochemical reactions of the cell. Theelectrochemical reaction at the electrodes involves conversion of ionsin atomic or molecular forms that migrate from the anode to the cathode.Thus, nonaqueous electrolytes suitable for the present invention aresubstantially inert to the anode and cathode materials, and they exhibitthose physical properties necessary for ionic transport, namely, lowviscosity, low surface tension and wettability.

[0035] A suitable electrolyte has an inorganic, ionically conductivesalt dissolved in a nonaqueous solvent, and more preferably, theelectrolyte includes an ionizable alkali metal salt dissolved in amixture of aprotic organic solvents comprising a low viscosity solventand a high permittivity solvent. The inorganic, ionically conductivesalt serves as the vehicle for migration of the anode ions tointercalate or react with the cathode active material. Preferably, theion forming alkali metal salt is similar to the alkali metal comprisingthe anode.

[0036] In the case of an anode comprising lithium, the alkali metal saltof the electrolyte is lithium based salt. Known lithium salts that areuseful as a vehicle for transport of alkali metal ions from the anode tothe cathode include LiPF₆, LiBF₄, LiAsF₆, LiSbF₆, LiClO₄, LiO₂, LiAlCl₄,LiGaCl₄, LiC(SO₂CF₃)₃, LiN(SO₂CF₃)₂, LiSCN, LiO₃SCF₃, LiC₆F₅SO₃,LiO₂CCF₃, LiSO₆F, LiB(C₆H₅)₄, LiCF₃SO₃, and mixtures thereof.

[0037] Low viscosity solvents useful with the present invention includeesters, linear and cyclic ethers and dialkyl carbonates such astetrahydrofuran (THF), methyl acetate (MA), diglyme, trigylme,tetragylme, dimethyl carbonate (DMC), 1,2-dimethoxyethane (DME),1,2-diethoxyethane (DEE), 1-ethoxy,2-methoxyethane (EME), ethyl methylcarbonate, methyl propyl carbonate, ethyl propyl carbonate, diethylcarbonate, dipropyl carbonate, and mixtures thereof. Suitable highpermittivity solvents include cyclic carbonates, cyclic esters andcyclic amides such as propylene carbonate (PC), ethylene carbonate (EC),butylene carbonate (BC), acetonitrile, dimethyl sulfoxide, dimethyl,formamide, dimethyl acetamide, γ-valerolactone, γ-butyrolactone (GBL),N-methyl-pyrrolidinone (NMP), and mixtures thereof. In the presentinvention, the preferred anode is lithium metal and the preferredelectrolyte is 0.8M to 1.5M LiAsF₆ or LiPF₆ dissolved in a 50:50mixture, by volume, of propylene carbonate as the preferred highpermittivity solvent and 1,2-dimethoxyethane as the preferred lowviscosity solvent.

[0038] The preferred form of a primary alkali metal/solid cathodeelectrochemical cell is a case-negative design wherein the anode is incontact with a conductive metal casing and the cathode contacted to acurrent collector is the positive terminal. The cathode currentcollector is in contact with a positive terminal pin via a lead of thesame material as the current collector. The lead is welded to both thecurrent collector and the positive terminal pin for electrical contact.

[0039] A preferred material for the casing is titanium althoughstainless steel, mild steel, nickel-plated mild steel and aluminum arealso suitable. The casing header comprises a metallic lid having anopening to accommodate the glass-to-metal seal/terminal pin feedthroughfor the cathode electrode. The anode electrode is preferably connectedto the case or the lid. An additional opening is provided forelectrolyte filling. The casing header comprises elements havingcompatibility with the other components of the electrochemical cell andis resistant to corrosion. The cell is thereafter filled with theelectrolyte solution described hereinabove and hermetically sealed suchas by close-welding a titanium plug over the fill hole, but not limitedthereto. The cell of the present invention can also be constructed in acase-positive design.

[0040] It is appreciated that various modifications to the inventiveconcepts described herein may be apparent to those of ordinary skill inthe art without departing from the spirit and scope of the presentinvention as defined by the appended claims.

What is claimed is:
 1. A cathode for an electrochemical cell, thecathode comprising an ε-phase silver vanadium oxide characterized asprepared by heating a silver vanadium compound mixed with a metal saltto form a reaction mixture heated to at least one reaction temperaturein an oxidizing atmosphere to produce the e-phase silver vanadium oxidehaving the formula Ag₂V₄O₁₁.
 2. The cathode of claim 1 wherein thesilver vanadium compound is γ-phase silver vanadium oxide having theformula Ag_(1.2)V₃O_(8.1).
 3. The cathode of claim 1 wherein the metalsalt is selected from the group consisting of silver lactate, silvertriflate, silver pentafluoropropionate, silver laurate, silvermyristate, silver palmitate, silver stearate, silver vanadate, silveroxide, silver carbonate, copper oxide, copper carbonate, manganesecarbonate, manganese oxide, magnesium carbonate, magnesium oxide, andcombinations and mixtures thereof.
 4. The cathode of claim 1 wherein themetal salt is Ag₂O and the ε-phase silver vanadium oxide has a BETsurface area of about 0.54 m²/g.
 5. The cathode of claim 1 wherein themetal salt is Ag₂CO₃ and the ε-phase silver vanadium oxide has a BETsurface area of about 0.44 m²/g.
 6. The cathode of claim 1 wherein thereaction mixture is heated to the at least one reaction temperature in arange from about 300° C. to about 550° C.
 7. The cathode of claim 1wherein the reaction mixture is heated to the at least one reactiontemperature for about 5 hours to about 30 hours.
 8. The cathode of claim1 further comprising a binder and a conductive material.
 9. A cathodefor an electrochemical cell, the cathode comprising an electrode activematerial characterized as prepared from γ-phase silver vanadium oxidehaving the formula Ag_(1.2)V₃O_(8.1) mixed with a metal salt compound toform a reaction mixture heated to at least one reaction temperature inan oxidizing atmosphere to produce the electrode active materialselected from the group consisting of Ag₂V₄O₁₁,Cu_(0.2)Ag_(0.8)V₂O_(5.6), Mn_(0.2)Ag_(0.8)V₂O_(5.8), andMg_(0.2)Ag_(0.8)V₂O_(5.6).
 10. The cathode of claim 9 wherein the metalsalt is selected from the group consisting of silver lactate, silvertriflate, silver pentafluoropropionate, silver laurate, silvermyristate, silver palmitate, silver stearate, silver vanadate, silveroxide, silver carbonate, copper oxide, copper carbonate, manganesecarbonate, manganese oxide, magnesium carbonate, magnesium oxide, andcombinations and mixtures thereof.
 11. The cathode of claim 9 whereinthe metal salt is Ag₂O such that the product electrode active materialhaving the formula Ag₂V₄O₁₁ has a BET surface area of about 0.54 m²/g.12. The cathode of claim 9 wherein the metal salt is Ag₂CO₃ such thatthe product electrode active material having the formula Ag₂V₄O₁₁ has aBET surface area of about 0.44 m²/g.
 13. The cathode of claim 9 whereinthe metal salt is CuO such that the product electrode active materialhaving the formula Cu_(0.2)Ag_(0.8)V₂O_(5.6) has a BET surface area ofabout 0.31 m²/g.
 14. A nonaqueous electrochemical cell, comprising: a)an anode; b) a cathode containing an active material comprising anε-phase silver vanadium oxide compound characterized as having beenprepared from a mixture of a silver vanadium compound and a metal saltforming a reaction mixture heated to at least one reaction temperaturein an oxidizing atmosphere to produce the ε-phase silver vanadium oxidehaving the formula Ag₂V₄O₁₁; c) a non-aqueous electrolyte activating theanode and the cathode; and d) a separator material electricallyinsulating the anode from the cathode, and of a porosity to allow forelectrolyte flow.
 15. The electrochemical cell of claim 14 wherein theanode is comprised of lithium.
 16. The electrochemical cell of claim 14wherein the silver vanadium containing compound is γ-phase silvervanadium oxide having the formula Ag_(1.2)V₃O_(8.1).
 17. Theelectrochemical cell of claim 14 wherein the metal salt is selected fromthe group consisting of silver lactate, silver triflate, silverpentafluoropropionate, silver laurate, silver myristate, silverpalmitate, silver stearate, silver vanadate, silver oxide, silvercarbonate, copper oxide, copper carbonate, manganese carbonate,manganese oxide, magnesium carbonate, magnesium oxide, and combinationsand mixtures thereof.
 18. The electrochemical cell of claim 14 whereinthe metal salt is Ag₂O and the ε-phase silver vanadium oxide has a BETsurface area of about 0.54 m²/g.
 19. The electrochemical cell of claim14 wherein the metal salt is Ag₂CO₃ and the ε-phase silver vanadiumoxide has a BET surface area of about 0.44 m²/g.
 20. The electrochemicalcell of claim 14 wherein the reaction mixture is heated to the at leastone reaction temperature in a range from about 300° C. to about 550° C.21. The electrochemical cell of claim 14 wherein the reaction mixture isheated to the at least one reaction temperature for about 5 hours toabout 30 hours.